Vortex evaporator



y 25, 1967 E. L... LUSTENADER 3,332,401

VORTEX EVAPORATOR Filed April 15, 1966 FIG.2

CONSTANT ENTHALPY ENTHALPY ENTROPY lNVENTORZ EDWARD L. LUSTENADER,

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7 5 TIQRNEY- United States Patent 3,332,401 VORTEX EVAPORATOR Edward L. Lustenader, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Filed Apr. 15, 1966, Ser. No. 542,951 6 Claims. (Cl. 12231) ABSTRACT OF THE DISQLOSURE Flash evaporation effected in vortex of saturated vapor by introducing liquid spray into superheat region near core of vortex. Unevaporated liquid concentrate is collected within vortex before reentering total vapor stream.

This invention relates to an improved device for evaporating liquid within a stream of relatively low pressure, low temperature saturated vapor with means for collecting unevaporated liquid before it enters the total vapor stream. More particularly, the invention relates to an improved means for effecting flash evaporation of raw feedwater in saturated steam without contaminating the steam, so as to produce fresh water for boiler feed makeup or other uses in connection with a steam turbine powerplant.

Flash distillation plants are known wherein low pressure, low temperature steam is extracted from the turbine to operate the distillation equipment. The energy costs associated with the distillation portion of the cycle become less if the extracted steam is at a lower pressure and temperature. If the steam can be used just as it enters the condenser, there is essentially no energy cost associated with distillation of the water since this energy would normally be discharged to the cooling water. However, the lower the pressure and temperature of extracted steam, the more expensive and complicated the distillation equipment required. Known techniques for effecting evaporation in saturated vapor entail reduction of the vapor pressure so that the vapor is in a superheated condition, in order that evaporation can take place therein from a spray or thin film. This reduction in vapor pressure is often not recoverable.

It would be desirable to effect evaporation in saturated vapor with as little a total pressure drop as possible, so as to enable use of saturated vapor at lower temperature and pressure. Means must be provided to prevent unevaporated raw liquid from re-entering and contaminating the stream if distillation is an object of the foregoing evaporation.

Accordingly, one object of the present invention is to provide an improved vortex evaporator for effecting evaporation in a saturated vapor with as low a pressure drop as possible.

Another object of the invention is to provide means for evaporating raw liquid in a saturated vapor flow and collecting the unevaporated concentrate.

Still another object of the invention is to carry out a distillation process in a relatively simple, inexpensive device with little loss in pressure thereacross.

A more specific object of the invention is to provide an improved device for obtaining distilled water for boiler makeup feed or other purposes from raw feedwater in a steam powerplant using saturated steam at relatively low temperature and pressure.

The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is a simplified schematic view of a steam tur- 3,332,4M Patented July 25, 1967 ice bine powerplant incorporating therein a vortex evaporator shown in an enlarged simplified view, partly in cross section, and

FIG. 2 is a modified Mollier diagram illustrating thermodynamic and fluid flow aspects within the vortex evaporator.

Briefly stated, the invention is practiced by providing a cylindrical conduit with swirl vanes therein for producing a vortex flow and deswirl vanes for straightening the flow. Means are provided to introduce a liquid spray near the core of the vortex. An inner flow isolating cylinder receives the spray and includes collecting slots for removing unevaporated liquid.

Referring to FIG. 1 of the drawing, a steam powerplant in-cludes a boiler 1 supplying steam to a high pressure turbine 2 whence it flows to a double-flow low pressure turbine 3. Saturated steam is collected in condenser 4, condensed by cooling heat exchanger 5 and collected in hot well 6. Boiler feed pump 7 pumps feedwater through feedwater heaters 812 in the usual manner. Between high pressure turbine 2 and low pressure turbine 3 is a vortex separator 13 of the general type which is modified to provide the present invention. Vortex separator 13 includes swirl vanes 14, deswirl vanes 15, and an annular collecting chamber 16 for removing water droplets. Details of such a vortex separator are disclosed in abandoned application, Serial No. 356,263 filed in the name of E. L. Lustenader on March 31, 1964.

A vortex evaporator, consisting of the basic vortex separator structure modified in accordance with the present invention, includes a cylindrical casing 17, in which are disposed a group of radially extending circumferentially spaced swirl vanes 18 mounted between a flow guiding member 19 and the wall of casing 17. Normally there would be six to eight such vanes, but a fewer number is shown to avoid obscuring the other details. Vanes 18 are curved to impart a vortex swirl to the saturated steam entering the inlet 20 via conduit 21 from the low pressure turbine.

At the other end of casing 17 is a series of oppositely curved swirl vanes 22 mounted on a flow guiding member 23 in a similar fashion. Vanes 22 are curved to remove the vortex swirl and to reestablish the normal radial pressure distribution across casing 17, thereby resulting in a low overall pressure drop through casing 17 Disposed between swirl vanes 18 and deswirl vanes 22 is a cylindrical flow isolating member 24 which is open at either end. Member 24 incorporates an annular collecting slot 25 surrounded by an annular collecting chamber 26 which will collect liquid droplets, removing them through pipe 27. Pump 28 may be provided to assist removal of the concentrate.

Means are provided for introducing a liquid spray into the interior of flow isolating member 24 by means of a spray nozzle 29 supplied through the center of the flow guiding member 19 by a pipe 30. Pipe 30 is connected to receive raw liquid from condenser cooler 5 after the liquid has been heated by passing through the condenser. It remains to, note that the outlet of casing 17 is connected to return fluid (with the added makeup of distilled vapor) to the cycle, such as by first heating feedwater in heaters 8 and 9 and then returning to hot well 6.

The operation of the invention will be described by reference to FIG. 2 which is a modified Mollier diagram in the region of operation of the vortex evaporator. Line 31 is the saturation line, above which the vapor is in a superheated condition and below which it is in a wet condition. Expansion of the steam through-low pressure turbine 3 results in wet steam in conduit 21 (FIG. 1) at a steam quality repersented by point 32 on the graph. At inlet 20 of casing 17, the radial pressure gradient of the fluid flowing therein is realtively uniform. However, the imposition of a vortex swirl on the fluid by swirl vanes 18 causes a redistribution of the radial pressure gradient such that a relatively low pressure exists at the core of the vortex which increases nonlinearly in a radial direction toward the wall of casing 17. Also any liquid droplets in the vapor are moved to the wall of casing 17 by centrifugal force and can be disregarded for the purpose of analysis, these droplets moving along the wall toward the outlet.

Lines 33, 34, 35 are constant pressure lines on the Mollier chart, only the ones being shown which are pertinent to an understanding of the invention. After disregarding the liquid droplets removed to the wall of casing 17, the portion of the saturated vapor at the wall can be represented by point 36 on the graph. The remainder of the vapor is at a condition represented by a series of points (passing radially toward the axis) on constant enthalpy line 37. Steam condition at the axis of the vortex is therefore represented by point 38 on the graph.

Depending upon the diameter of the inner flow isolating cylinder 24, pressure at the wall of cylinder 24 is represented by a point 39 on the constant enthalpy line.

It will be apparent, therefore, that a region exists, indicated by cross hatching on the graph, within which the vapor is in a superheated condition and isolated from the remainder of the flow, this isolated superheat region being bounded by constant pressure lines at the axis and at wall 24, by the constant enthalpy line 37, and by saturation line 31 (or by points 3S41).

Raw liquid heated to the proper temperature by condenser cooler is sprayed into the flashing region by nozzle 29 in such a manner that the droplets are contained within cylinder 24 (FIG. 1). The proper temperature of the raw liquid is preferably 2 or 3 degrees F above the saturation temperatures corresponding to the vortex core or flashing region pressures, points 40 and 41 in FIG. 2. Flashing takes place and any unevaporated coucentrate is removed through slot 25 and pi e 27 due to the vortex centrifugal field. Some slight pressure drop will occur due to the need for the fluid to accelerate the flashed vapor and the raw liquid spray.

The vapor in cylinder 24, consisting of the originally isolated vapor and the flashed vapor, re-enters the total saturated vapor stream at the outlet of cylinder 24 to provide an augmented vapor flow. The vortex swirl is then removed from the augmented flow by deswirl vanes 22 to reestablished the normal radial pressure gradient in the fluid, thereby reducing the total overall pressure drop through the vortex evaporator.

In the foregoing manner, an additional mass flow of distilled water is added to the feedwater, This can be used for boiler makeup feed, or, depending upon the design, sufficient additional pure water may be added to permit withdrawing distilled water from the cycle. The total cost to the cycle of the arrangement shown is very loW since steam at a very low temperature and pressure is employed at a condition which would usually be unavailable for this purpose.

The invention, of course, is not limited to a steam plant but is merely shown therein for purposes of illustration. The device is applicable to any fluid process wherein it is desired to utilize relatively low pressure vapor to perform evaporation of additional liquid in order to obtain distilled liquid or additional vapor without contami nating the main flow.

While there has been shown what is considered to be the preferred embodiment of the invention, other modifications will occur to those skilled in the art. It is, of course, intended to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A vortex evaporator comprising:

a source of saturated vapor,

means for providing vortex flow of said vapor,

means for isolating a superheated portion of the flow near the core of the vortex,

means introducing liquid spray into said isolating means at a temperature suitable for flash evaporation by said superheated portion within the isolating means, and

collecting means associated with the isolating means for removing unevaporated liquid spray from within the isolating means.

2. The combination according to claim 1 which includes means arranged to recombine the isolated vapor portion and the evaporated portion of the liquid spray with the remainder of the vapor to provide an augmented vapor vortex flow and including additional means removing the vortex swirl from the augmented vapor.

3. The combination according to claim 1, wherein said isolating means comprises a cylinder disposed coaxial with the axis of the vortex and wherein said collecting means comprises an annular slot with an annular surrounding collecting chamber disposed intermediate the ends of said cylinder.

4. The combination according to claim 1, wherein said vortex-providing means comprises a set of radial swirl vanes disposed in an outer cylinder and wherein said isolating means comprises an inner cylinder coaxial with the outer cylinder and downstream from the swirl vanes.

5. The combination according to claim 1, wherein said vortex-providing means includes a set of swirl vanes disposed within an outer cylinder on a stationary flow guiding member coaxial with the cylinder, and wherein said spray-introducing means comprises a liquid spray nozzle disposed on said flow guiding member, and wherein said isolating means comprises an open-ended inner cylinder coaxial with the outer cylinder and disposed to receive substantially all of the spray from said nozzle.

6. A vortex evaporator comprising:

a source of saturated steam,

an outer cylindrical member connected to receive steam from said source,

a flow guiding member disposed on the axis of the outer cylindrical member and having a set of radially extending swirl vanes attached between it and the cylidnrical member for imparting a vortex swirl to the steam,

a spray nozzle disposed on the flow guiding member downstream of the swirl vanes and connected to receive water from a source under pressure,

an inner cylindrical member open at either end disposed coaxially with the outer member so as to receive substantially all of the spray from said nozzle,

an annular slot in the wall of said inner cylindrical member intermediate its ends,

an annular collecting chamber disposed around said slot for removing unevaporated liquid spray, and

a set of radial deswirl vanes located downstream from the inner cylindrical member and arranged to remove vortex swirl from the steam.

References Cited UNITED STATES PATENTS 2,201,301 5/1940 Richardson 55-397 2,315,226 3/1943 Rohlin l22459 2,398,048 4/1946 Schmidt 122459 X KENNETH W. SPRAGUE, Primary Examiner. 

